This invention relates to the field of abrasive waterjet cutting. More specifically, the invention relates to a system allowing for the controlled use of abrasive transferred to the cutting surface in a liquid slurry format.
Waterjet cutting of materials consists of focusing a coherent stream of water under high pressure (10,000-125,000 PSI) through a small (0.003-0.063″) opening against a surface to be cut. The velocity of the water stream is directly proportional to the pressure differential across the opening in the jewel (Ruby, Sapphire or Diamond) placed in the entry face of the focusing nozzle. Soft materials such as plastics, fabrics and wood are successfully cut by this method. Hard materials such as steel, concrete and ceramics can be readily cut up to a depth of 12″ by adding abrasive particles to the accelerated water stream (Abrasive Waterjet) prior to exiting the focusing tube at speeds several times greater than the speed of sound.
Current systems for employing abrasive particles as an aid to waterjet cutting of materials almost exclusively consist of a dry abrasive supplied to the mix/focusing tube of a waterjet cutting nozzle by virtue of induced venturi pressure drawing dry abrasive granules from a supply hopper located in close proximity to the cutting head. Compressed air pressure is applied to the supply mini hopper to aid in the transfer of dry granules to the cutting head as a result of the venture effect. As distance from the supply hopper to the venturi source is increased, dry abrasive tends to clog the entry tube resulting in uneven abrasive mixing or total blockage of the abrasive entry. In many cases, the uneven feed causes blockage in the focusing tube causing liquid backup into the entry tube and supply hopper. Attempts to introduce abrasive granules in the form of a slurry have been largely unsuccessful due to settling of abrasive out of suspension in the water. Major problems with controlling abrasive delivery rate in processes attempted to date have frustrated all attempts to adopt a successful slurry feed system for use in this industry.